C LINICAL P RACTICE

Endodontic Therapy in a 3-Rooted Mandibular First Molar: Importance of a Thorough Radiographic Examination

• Juan J. Segura-Egea, DDS, MD, PhD • • Alicia Jiménez-Pinzón, DDS • • José V. Ríos-Santos, DDS, MD, PhD •

Abstract

This case report describes endodontic therapy on a mandibular first molar with unusual root morphology. In the initial treatment the working length had been determined with only an apex locator; no periapical radiographs had been obtained because the patient was pregnant. The root canal into an additional distolingual root had not been found and was therefore left untreated, which led to treatment failure after 11 months. The radiographic examina- tion performed in a subsequent endodontic treatment allowed detection of the anomalous root and completion of the root canal treatment. The distolingual root canal would have been identified during the initial endodontic therapy if a thorough radiographic examination had been carried out. This report highlights the importance of radiographic examination and points out the need to look for additional canals and unusual canal morphology associated with a mandibular first molar. Radiographic examination during pregnancy is also discussed.

MeSH Key Words: dental care; molar/anatomy and histology; tooth root/anatomy and histology; pregnancy

© J Can Dent Assoc 2002; 68(9):541-4 This article has been peer reviewed.

oot canals may be left untreated during endodontic Thai origin had a third distolingual root. The additional therapy if the dentist fails to identify their presence, root is generally located on the lingual aspect and has a particularly in teeth with anatomical variations or Vertucci type I canal configuration.2 Such a variant has not R 1 extra root canals. Therefore, a thorough radiographic been reported for the mandibular second molar, but it is examination, including preoperative radiographs, is essen- found (rarely) in the mandibular third molar.7 tial for success in endodontic therapy. An apex locator can This report describes endodontic therapy on a 3-rooted help in determining the working length during root canal mandibular first molar. The canal in the additional treatment, but it cannot replace periapical radiography distolingual root was left untreated during initial endodon- because it does not provide the detailed information about tic treatment because radiographic examination was not root canal morphology that radiography does. carried out at that time. Anatomical variations are an acknowledged characteris- tic of mandibular permanent molars.2,3 Most mandibular Case Report first and second molars in Caucasians have 2 roots, with A 34-year-old Caucasian woman in good health sought 2 mesial canals and 1 distal canal.4,5 The presence of a third treatment for pain in the region of the right mandibular root in the permanent first molar is the major variant in this first molar. The patient had undergone endodontic therapy group. The frequency of this trait is less than 5% in of the same tooth 11 months earlier, when she was Caucasian, African, Eurasian and Indian populations, 4 months pregnant. At that time, she had asked her dentist whereas it occurs in 5% to more than 40% of people of to perform the root canal treatment without radiographic Mongolian origin.6 Gulabivala and others7 recently examination because of the pregnancy. Therefore, the reported that 13% of mandibular first molars in people of dentist had used only an apex locator to determine the

Journal of the Canadian Dental Association October 2002, Vol. 68, No. 9 541 Segura-Egea, Jiménez-Pinzón, Ríos-Santos

Figure 1: Preoperative radiograph shows that the right mandibular Figure 2: Periapical radiograph shows tooth length; a K-file #25 is permanent first molar (tooth 46) has an additional distolingual root evident in the additional distolingual root. and that its root canal has not been treated endodontically.

working length. During the current presentation, Michigan). The apical two-thirds of the gutta percha and the patient reported recent spontaneous pain around the sealer combination were re-treated with conventional hand apical area of the tooth, as well as pain upon mastication. files and chloroform. Aliquots of 0.05 mL of chloroform Clinical examination of the right mandibular first molar were injected into the canal to soften the gutta percha. revealed a disto-occlusal silver amalgam restoration and a Hedstrom files (size 25 to 45; Dentsply Maillefer) were mesio-occlusal resin composite restoration. The tooth was used for re-treatment of the working length. During the discoloured and was sensitive to percussion and palpation. re-treatment, the root canal was constantly irrigated with A periapical radiograph (Fig. 1) showed that the tooth had 5% NaOCl. The criteria for completion of re-treatment a total of 3 roots; the 2 canals of the mesial root and the were the cleanliness of the filings, absence of gutta percha or single canal of 1 of the distal roots had all been treated sealer on the files or the paper points, and smoothness of endodontically, but the canal of the second distal root had the canal walls. not been treated, probably because the dentist failed to For both the distobuccal and distolingual roots, the identify its presence. The radiograph revealed radiolucency canals were instrumented to one size larger than the previ- in the periapical area of the distolingual root and apparent ous master apical file used. The root length was estimated widening of the periodontal ligament space of this with an apex locator (Root ZX, Morita, Tokyo, Japan) and additional root. Radiography also revealed double peri- confirmed with periapical radiography (Fig. 2). odontal ligament (PDL) spaces in the mesial root. The After being cleaned and shaped, the canals were dried apical portion of the distobuccal canal seemed to be and obturated by cold lateral condensation of gutta percha infraobturated. (Dentsply Maillefer) and sealer (AH Plus, Dentsply DeTrey, Observation via a conventional access cavity revealed the Konstanz, Germany), and the tooth was filled with resin presence of 3 canal orifices, 2 mesial and 1 distobuccal, all composite (Fig. 3). of them filled with gutta percha. The access cavity was At follow-up 14 months later, the tooth was asympto- enlarged distolingually by means of an Endo-Z bur matic and there was radiographic evidence of progressive (Dentsply Maillefer, Ballaigues, Switzerland). Careful inves- periapical healing (Fig. 4). The tooth was completely tigation of the pulp chamber with a K-file #15 (Dentsply asymptomatic at 2 years. Further radiographic examination Maillefer) and ethylenediaminetetraacetic acid (EDTA; showed that the left mandibular permanent first molar of Glyde File Prep, Dentsply Maillefer) revealed a distolingual this patient also had 3 roots (Fig. 5). Moreover, double orifice with 1 canal. Coronal flaring was accomplished with PDL spaces were also present in the mesial root of this Gates Glidden burs (sizes 3 and 4) (Dentsply Maillefer). tooth. The distolingual canal was cleaned and shaped by hand with K-Flexofiles (Dentsply Maillefer), with a balanced Discussion force action under irrigation with 5% sodium hypochlorite This report describes initial failure of endodontic ther- (NaOCl) and EDTA. apy in a 3-rooted right mandibular permanent first molar. The distobuccal canal was re-treated to achieve better The fourth root canal, which occurred in a supernumerary obturation. The cervical third of the gutta percha was distolingual root, was not identified during the first treat- removed with a heated 5/7 plugger (Kerr/Sybron, Romulus, ment because periapical radiography was not performed;

542 October 2002, Vol. 68, No. 9 Journal of the Canadian Dental Association Endodontic Therapy in a 3-Rooted Mandibular First Molar: Importance of a Thorough Radiographic Examination

Figure 3: Postoperative radiograph shows the endodontically treated Figure 4: Radiograph obtained at 14-month follow-up. The tooth was distolingual canal and the re-treated distobuccal canal. asymptomatic. Double periodontal ligament spaces are visible in the mesial root, which suggests root bifurcation.

root is smaller than the distobuccal root and is usually curved.13 In the case reported here the trait occurred bilat- erally, and both of the extra distolingual roots seemed to be smaller than their respective distobuccal roots. The number of roots in the mandibular first molar may be increased not only by the presence of a distolingual root, but also through bifurcation of the mesial root, a trait found in 0.5% of mandibular permanent first molars.14 In the case reported here, periapical radiographs of both the right and left mandibular permanent first molars revealed double PDL spaces in the mesial roots. This trait could be interpreted in 3 ways: bifurcation of the mesial root, presence of 2 mesial roots or a very broad faciolingually Figure 5: Periapical radiograph shows the left mandibular permanent oriented mesial root. The most probable cause in this first molar with an additional distal root. Double periodontal ligament patient was bifurcation of the mesial root.14 spaces are visible in the mesial root of this tooth, which again suggests root bifurcation. Knowledge of both normal and abnormal anatomy of the molars dictates the parameters for execution of root this canal was therefore left untreated. Eventual treatment canal therapy and can directly affect the probability of success was achieved by endodontic therapy of this extra success. Therefore, practitioners must be familiar with all canal and re-treatment of the distobuccal canal. molar abnormalities, as well as their prevalence. The 3-rooted mandibular first molar reported here In the case presented here, initial endodontic therapy had 1 mesial root with 2 canals and 2 distal roots with a was unsuccessful because of the dentist’s failure to identify single canal each. This structure is the same as that of other the fourth canal in the additional root, as well as inadequate 3-rooted mandibular first molars described previously.8 obturation of the distobuccal canal. The distolingual The roots and canals of mandibular permanent first canal would have been identified during the first visit if a molars have several typical anatomical features, as well as a thorough radiographic examination had been carried great number of anomalies. The presence of 4 canals is out. However, the patient was pregnant and asked that relatively frequent,6 but the presence of 2 distal roots is radiography not be performed. Pregnancy is not an uncommon.9 Using radiographic examination, Steelman10 absolute contraindication to dental radiography.15 A preg- found that 10 (6.4%) of 156 Hispanic children had an nant patient’s exposure to dental X-rays should be limited accessory distal root of the mandibular permanent first to what is required for treatment to be rendered immedi- molar. The prevalence of an extra root is about equal in ately (while the patient is pregnant),16 but the absorbed males and females, but the anomaly is more frequent on the radiation dose to the pelvic region from a full-mouth left side.11 An additional distolingual root occurred unilat- series of dental radiographs, if done properly, is only about erally in approximately 40% of the cases summarized by 1 µGy (0.1 mrad). For comparison, for the U.S. popula- Quackenbush,12 predominantly on the right side. The extra tion, the average annual dose of radiation from natural

Journal of the Canadian Dental Association October 2002, Vol. 68, No. 9 543 Segura-Egea, Jiménez-Pinzón, Ríos-Santos

environmental sources is about 0.8 mGy or 800 µGy 14. Onda S, Minemura R, Masaki T, Funatsu S. Shape and number of the 17 roots of the permanent molar teeth. Bull Tokyo Dent Coll 1989; (80 mrad). Thus, the dose from typical periapical radiog- 30(4):221-31. raphy is equivalent to about one-half day of unavoidable 15. Livingston HM, Dellinger TM, Holder R. Considerations in the exposure to natural background radiation. Moreover, management of the pregnant patient. Spec Care Dentist 1998; 18(5):183-8. during dental radiography, as for most other types of radi- 16. Lee A, McWilliams M, Janchar T. Care of the pregnant patient in the dental office. Dent Clin North Am 1999; 43(3):485-94. ography, the radiation source is focused on the area being 17. Lubenau JO. Unwanted radioactive sources in the public domain: a imaged and there is virtually no exposure to any body part historical perspective. Health Phys 1999; 76(2 Suppl):S16-22. other than the part of interest. 18. Walker RT, Quackenbush LE. Three-rooted lower first permanent This case highlights the importance of radiographic molars in Hong-Kong Chinese. Br Dent J 1985; 159(9):298-9. 19. Somogyi-Csizmazia W, Simons AJ. Three-rooted mandibular first examination, especially preoperative radiography, for molars in Alberta Indian children. J Can Dent Assoc 1971; 37(3):105-6. success in endodontic therapy. Although uncommon, an extra root containing an independent canal may be present. The third root is radiographically evident in about 90% of cases,18 but may be difficult to see because of its slender dimensions. In such cases, vertically and horizontally angled views may be helpful.19 C

Dr. Segura-Egea is an associate professor in the department of stoma- tology, school of dentistry, University of Seville, Seville, Spain. Dr. Jiménez-Pinzón is a doctoral fellow in the department of stoma- tology, school of dentistry, University of Seville, Seville, Spain. Dr. Rios-Santos is a lecturer in the department of stomatology, school of dentistry, University of Seville, Seville, Spain. Correspondence to: Dr. Juan J. Segura-Egea, C/Cueva de Menga nº 1, portal 3, 6º-C 41020-SEVILLA, SPAIN. E-mail: segurajj@ wanadoo.es. The authors have no declared financial interests in any company manufacturing the types of products mentioned in this article.

References 1. Reeh ES. Seven canals in a lower first molar. J Endod 1998; 24(7):497-9. 2. Sperber GH, Moreau JL. Study of the number of roots and canals in Senegalese first permanent mandibular molars. Int Endod J 1998; 31(2):117-22. 3. Sidow SJ, West LA, Liewehr FR, Loushine RJ. Root canal morphology of human maxillary and mandibular third molars. J Endod 2000; 26(11):675-8. 4. Barker BC, Parsons KC, Mills PR, Williams GL. Anatomy of root canals. III. Permanent mandibular molars. Aust Dent J 1974; 19(6):408-13. 5. Vertucci FJ, Williams RG. Root canal anatomy of the mandibular first molar. J N J Dent Assoc 1974; 45(3):27-8. 6. Gulabivala K, Aung TH, Alavi A, Ng YL. Root and canal morphology of Burmese mandibular molars. Int Endod J 2001; 34(5):359-70. 7. Gulabivala K, Opasanon A, Ng YL, Alavi A. Root and canal morphol- ogy of Thai mandibular molars. Int Endod J 2002; 35(1):56-62. 8. Kimura Y, Matsumoto K. Mandibular first molar with three distal root canals. Int Endod J 2000; 33(5):468-70. 9. Prabhu NT, Munshi AK. Additional distal root in permanent mandibular first molars: report of a case. Quintessence Int 1995; 26(8):567-9. 10. Steelman R. Incidence of an accessory distal root on mandibular first permanent molars in Hispanic children. ASDC J Dent Child 1986; 53(2):122-3. 11. Loh HS. Incidence and features of three-rooted permanent mandibu- lar molars. Aust Dent J 1990; 35(5):434-7. 12. Quackenbush LE. Mandibular molar with three distal root canals. Endod Dent Traumatol 1986; 2(1):48-9. 13. Weine FS. Access cavity preparation and initiating treatment. In: Weine FS, editor. Endodontic therapy, 3rd ed. St. Louis, MO: The C. V. Mosby Company; 1982. p. 207-55.

544 October 2002, Vol. 68, No. 9 Journal of the Canadian Dental Association